This invention relates to high voltage switching apparatus, and more particularly to a shunt capacitor switch having multiple arc regions, wherein one of the arc regions is connected in parallel with an impedance. This invention relates to a modification of the construction disclosed in U.S. Pat. No. 4,568,806 issued on Feb. 3, 1986 to Russell E. Frink. U.S. Pat. No. 4,568,806 relates to a puffer circuit interrupter with enhanced power handling capability.
Shunt capacitor banks are used to modulate or control the voltage levels on electric utility systems. Since the voltage level of a utility system varies from one part of a day to another, the capacitor banks are switched frequently. The energization of capacitor banks can result in high phase-to-phase surges in power system. When a capacitor bank is switched into a power system for purposes of energizing the capacitor bank, the capacitor bank initially draws a very high current from the system. This initially high current draw is due to the characteristic of an unenergized or uncharged capacitor to initially function similar to a zero resistance electrical element and subsequently function as a high resistance electrical element as it becomes fully energized.
Shunt capacitor banks are frequently switched by conventional circuit breakers, vacuum switches and circuit switches without any resistor or reactor pre-insertion capability. These devices are known to generate high levels of transient over voltages during the closing of the circuit for switching capacitor banks. Under certain circumstances, these transients may cause severe damage to costly equipment at substations where the capacitor bank are switched and at locations in utility systems other than the substations. Normally, equipment damaged includes power transformers and, in some cases, the capacitors and substation control circuitry.
Shunt capacitor banks are also switched by circuit switcher with resistor or reactor pre-insertion capability. These devices are widely used, but are generally recognized as not having 100% probability of performing as intended. Additionally, these devices periodically fail to commutate the arc through the resistor or reactor. Furthermore, upon closing, the pre-strike arc in air generates a loud noise. (See the HIGH VOLTAGE SWITCH WITH PRE-INSERSION RESISTOR of U.S. Pat. No. 3,576,414.)
In light of these problems it can be seen that it would be highly desirable to have a switching device adapted to initially impead the high current flow into a capacitor bank during energization.